Film carrier and method of manufacturing same

ABSTRACT

There is provided a film carrier comprising a resin base film and a rolled copper foil laminated thereon, said rolled copper foil forming leads for mounting semiconductor chips or other electronic components in place, characterized in that said rolled copper foil is made of a copper alloy composition consisting essentially of a total of 0.005 to 1.5% by weight of one or two or more selected from a group consisting of 
     
         ______________________________________                                    
 
    
     P     0.005-0.05                                                          
                wt %,    B    0.005-0.05                                  
                                       wt %,                              
Al    0.01-0.5  wt %,    As   0.01-0.5 wt %,                              
Cd    0.01-0.5  wt %,    Co   0.01-0.5 wt %,                              
Fe    0.01-0.5  wt %,    In   0.01-0.5 wt %,                              
Mg    0.01-0.5  wt %,    Mn   0.01-0.5 wt %,                              
Ni    0.01-0.5  wt %,    Si   0.01-0.5 wt %,                              
Sn    0.01-0.5  wt %,    Te   0.01-0.5 wt %,                              
Ag    0.01-1    wt %,    Cr   0.01-1   wt %,                              
Hf    0.01-1    wt %,    Zn   0.01-1   wt % and                           
Zn    0.01-1    wt %                                                      
______________________________________                                    
 
     and the remainder Cu with inevitable impurities, preferably with oxygen content of not more than 50 ppm. There is also provided a method for manufacturing a film carrier characterized in that the leads of the film carrier for mounting semiconductor chips or other electronic components in place are formed by the steps of providing a rolled copper alloy foil having the composition defined above, preferably strain relief annealing it after its final cold rolling and then laminating the annealed foil onto a resin base film followed by etching.

FIELD OF THE INVENTION

This invention relates to a film carrier having leads suited formounting and packaging semiconductor chips and other electroniccomponents on printed-circuit boards and also to a method ofmanufacturing the same.

BACKGROUND OF THE INVENTION

Semiconductor chips such as ICs and LSIs are usually as small as severalmillimeters square and about 100 microns thick and are difficult tomount as they are on printed-circuit boards. To facilitate the mounting,it is customary to contain each chip in a certain housing known as an ICor LSI package.

The IC or LSI package basically has a structure in which a semiconductorchip is attached to a heat sink, or a heat-radiating metal sheet, andelectrode terminals of the chip and leads for connection to externalcircuits are joined by bonding wires.

The leads project from the package like the legs of a centipede, and arealso called pins.

Such IC and LSI packages prevailing at present day are classified intotwo dominant types; dual in-line package (DIP) having two rows of pinsextending vertically downward from the package body at opposite sidesthereof and flat package (FP) with pins projecting from all four edgesof the package body in the same plane.

The FP type is advantageous over the DIP type because it can use somemore leads (pins) and thereby slightly increase the packaging density onprinted boards.

However, the recent tendency toward even higher degrees of integrationfor LSIs has accordingly increased the number of pins for the individualpackages. The FP and DIP types are both failing to keep up with thetendency, and there is a need for a new packaging system capable ofaccommodating the rapidly increasing number of pins.

In an effort to meet the requirement, a new mounting and packagingsystem using a "film carrier" (also known as tape carrier or tab) hasbeen developed.

The film carrier, as shown in FIG. 1, is based on a length of tape 2formed with sprocket holes 1. The tape 2, or the base using a polyimide,polyester, polyether sulfone (PES), polyparabanic acid (PPA) or suchlike resin, is covered with a copper foil. The foil in turn isphotoetched to provide copper inner leads (fingers for chip bonding) 3and copper outer leads (fingers for external connections) 4. The numeral5 indicates testing pads.

The inner leads 3, outer leads 4, and the like in a fine pattern arecollectively called leads in this specification.

The process steps in common use will now be described in some moredetail. The Polyimide or other resin base of a lengthy tape isperforated to provide device holes, a copper foil about 35 micron thickis laminated as a circuit-forming metal to the perforated tape, and thecopper foil is coated with a resist, a pattern is printed, exposed tolight, developed, and etched. After the removal of the resist and, wherenecessary, after an additional step of plating, a fine pattern of leadsas in FIG. 1 is formed.

As FIG. 1 illustrates, a fragment of the base film is punched in thecenter to provide a device hole for mounting a semiconductor chip or thelike, and leads formed from the copper foil are arranged in a highdensity in the hole to partly project thereinto. The width of the leadsis sometimes as narrow as several ten microns.

At the electrodes of a semiconductor chip there are usually formed bumpsfor connection to the inner leads on the film carrier. The electrodes(bumps) of the semiconductor chip and the inner leads of the filmcarrier are joined by the gang bonding method for simultaneousconnection of all terminals involved. When the leads are to be mountedon a printed-circuit board, the outer leads of copper foil are cut outtogether with the semiconductor element from the film carrier (bypunching) and then mounted on the printed board.

The tape carrier formed this way offers many advantages including thefollowing:

(1) It can be handled in the form of a (long) tape and preciselypositioned as desired using the sprocket holes.

(2) Unlike wire bonding, the bonding seldom deforms the inner leads andpermits the provision of terminals to a much finer pitch (on the orderof 80 microns).

(3) The gang bonding allows for a single-step bonding regardless of thenumber of terminals involved.

(4) Burn-in tests of the chips as attached to the carrier are possible.

(5) The thin, flexible carrier permits correspondingly thin, flexibletype of packages.

(6) The chips after packaging can be easily replaced.

This film carrier is particularly well suited for high-density packagetype LSIs that require larger numbers of pins than usual.

For the metal conductors (leads) to be used on the above film carrier,which are required to have high electrical conductivity, tough pitchcopper foils 20 to 50 μm thick have hitherto been employed. However, thetough pitch copper (pure copper) foils have number of drawbacks and nonehave proved satisfactory. In order to attain a high density arrangementof fine leads it is necessary to secure enhanced etching accuracy. Tothis end the copper foil must be made as thin as possible. Nevertheless,the fine copper leads, formed by photoetching the copper foil about 20to 50 μm thick as stated above, tend to soften on heating during thecourse of fabrication. Also they are easily deformed as the resist ispeeled off during etching of when the flow of plating solution changesor the film carrier comes in contact with rolls conveying it. Thedeformation of the fingers can lead to shorting of the terminals orimperfect bonding.

When a copper foil is bonded to a resin base with an adhesive, intimateadhesion between the foil and resin is obtained and reliability improvedby the use of a high curing temperature and an adhesive for hightemperature use. However, this involves a relatively long curing period(usually several hours) and presents a problem of easy softening of theordinary pure copper foils.

An additional disadvantage with the conventional rolled copper foilsforming the leads has been anisotropy in mechanical properties. Thereare sharp distinctions between their longitudinal (rolling direction)and lateral (normal to the rolling direction) tensile strengths andelongations.

In view of the foregoing and other considerations, the copper foil as ametal conductor on a tape carrier is required to possess the followingproperties:

(1) High electrical conductivity as a metal conductor.

(2) Toward the requirement for thinner foils, greater strength than purecopper, and no possibility of deformation during fabrication.

(3) Sufficient heat resistance to withstand the heat of approximately200° C. to be encountered during the manufacture of the tape carrier.

(4) No anisotropy in strength or heat resistance, which is essential forthe fingers extended in four directions.

(5) Smooth surface to permit the bonding of IC elements at the back ofthe fingers.

(6) Flatness of the shape for the same purpose as above.

(7) Ease of etching.

(8) Good adhesion to the resin involved.

As far as conventional tough pitch copper (pure copper basis) foilconcerned, it is impossible to satisfy with all requirements statedabove.

In this connection, tough pitch copper foils generally used have afollowing compositions:

Cu: 99.96-99.97 wt %

O₂ : 0.025-0.035 wt %

concomitant impurities: not more than 0.05 wt % (Fe, Pb, etc.)

OBJECT OF THE INVENTION

The object of this invention is to provide a film carrier which bringsimprovements in strength and heat resistance of the leads, thus makingthe reduction in their thickness possible, and eliminates the anisotropyof their mechanical properties, with the ability of being etched withincreased accuracy and meeting the growing requirement for high-densitymultipin arrangement, and also a method of manufacturing the same.

SUMMARY OF THE INVENTION

To accomplish the above object, it is necessary to enhance the strengthand heat resistance of a rolled copper foil used in a film carrier andsimultaneously to eliminate or lower the anisotropy of the copper foilby preventing the growing of (100) orientation which is recrystalizationtexture. Under many investigations, the inventors have obtained thefinding that the addition of one or more of P, B, Al, As, Cd, Co, Fe,In, Mg, Mn, Ni, Si, Sn, Te, Ag, Cr, Hf, Zn and Zr each in a specifiedamount is very effective for the above object. According to anotherfinding further obtained, it is perferable to suppress oxygen content tonot more than 50 ppm for further enhancing heat-resistance-improvingeffect by the aforementioned additive elements. Based on such findings,this invention provides a film carrier comprising a resin base film anda rolled copper foil laminated thereon said rolled copper foil formingleads for mounting semiconductor chips or other electronic components inplace, characterized in that said rolled copper foil is made of a copperalloy composition consisting essentially of a total of 0.005 to 1.5% byweight of one or two or more selected from a group consisting of

    ______________________________________                                        P     0.005-0.05                                                                              wt %,    B    0.005-0.05                                                                             wt %,                                  Al    0.01-0.5  wt %,    As   0.01-0.5 wt %,                                  Cd    0.01-0.5  wt %,    Co   0.01-0.5 wt %,                                  Fe    0.01-0.5  wt %,    In   0.01-0.5 wt %,                                  Mg    0.01-0.5  wt %,    Mn   0.01-0.5 wt %,                                  Ni    0.01-0.5  wt %,    Si   0.01-0.5 wt %,                                  Sn    0.01-0.5  wt %,    Te   0.01-0.5 wt %,                                  Ag    0.01-1    wt %,    Cr   0.01-1   wt %,                                  Hf    0.01-1    wt %,    Zn   0.01-1   wt % and                               Zn    0.01-1    wt %                                                          ______________________________________                                    

and the remainder Cu with inevitable impurities, preferably with oxygencontent of not more than 50 ppm. This invention also provides a methodfor manufacturing a film carrier characterized in that the leads of thefilm carrier for mounting semiconductor chips or other electroniccomponents in place are formed by the steps of providing a rolled copperallow foil having the composition defined above, preferably strainrelief annealing it after its final cold rolling and then laminating theannealed foil onto a resin base film followed by etching.

As additive elements, one or more of In, Ag and Sn is particularlypreferred.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic explanatory view of a typical film carrier; and

FIG. 2 is a graph showing the tensile strengths and elongations atvarying annealing temperatures of a copper alloy foil for use in thepresent invention and of a tough pitch copper foil.

DETAILED EXPLANATION OF THE INVENTION

The alloying ingredients of the rolled copper foil that constitutes thepresent inventions, namely, P, B, Al, As, Cd, Co, Fe, In, Mg, Mn, Ni,Si, Sn, Te, Ag, Cr, Hf, Zn, and Zr, all improve the strength and heatresistance of the copper. They also inhibit the development of the (100)orientation that is the recrystallized texture structure of copper, andthereby correct the anisotropy.

However, there are upper and lower limits to the percentages of thesealloying ingredients to be added, as will be elucidated below.

If the P or B content is less than 0.005% by weight, or the Al, As, Cd,Co, Fe, In, Mg, Mn, Ni, Si, Sn, Te, Ag, Cr, Hf, Zn, or Zr content isless than 0.01% by weight, the result will not be as satisfactory asexpected. Conversely if the P or B content is more than 0.05% by weight,or the Al, As, Cd, Co, Fe, In, Mg, Mn, Ni, Si, Sn, or Te content is morethan 0.5% by weight, or the Ag, Cr, Hf, Zn, or Zr content exceeds 1% byweight, a serious decrease in conductivity will result. The total amountof one or two or more ingredients selected from the above group isconfined within the range of 0.005 to 1.5% by weight. The lower limit of0.005% by weight is fixed for the addition of a single ingredient. Asregards the upper limit, the addition of two or more ingredients in acombined amount greater than 1% by weight does not always cause anappreciable decrease in conductivity due partly to the formation ofintermetallic compounds. Any amount in excess of 1.5% by weight,however, causes a serious conductivity drop.

Preferable amounts to be added are as follows:

    ______________________________________                                        P       0.007-0.02 wt %,                                                                            B        0.007-0.02 wt %,                               Al      0.05-0.2 wt %,                                                                              As       0.05-0.2 wt %,                                 Cd      0.05-0.2 wt %,                                                                              Co       0.05-0.2 wt %,                                 Fe      0.05-0.2 wt %,                                                                              In       0.02-wt %,                                     Mg      0.05-0.2 wt %,                                                                              Mn       0.05--0.2 wt %,                                Ni      0.05-0.2 wt %,                                                                              Si       0.05-0.2 wt %,                                 Sn      0.05-0.2 wt %,                                                                              Te       0.05-0.2 wt %,                                 Ag      0.05-0.5 wt %,                                                                              Cr       0.05-0.5 wt %,                                 Hf      0.05-0.5 wt %,                                                                              Zn       0.1-0.8 wt % and -Zn 0.05-0.5 wt               ______________________________________                                                                       %                                          

Among said additive elements, the addition of one or more of In, Ag andSn is preferable.

The material having addition of In or Sn to the alloy composition of thefoil that forms the leads is particularly excellent material with higherconductivity and controllability of the half-softening temperature inthe range of 200° to 300° C. [Here the term half-softening temperaturerefers to the temperature at which the copper material usually isdesired to soften when bonded with an IC chip (320° C.) and when joinedto a substrate (270° C.).] Moreover, it permits the copper material tobe easily etched away with the commonly employed etching solutions offerric chloride (FeCl₃) or copper chloride (CuCl₂).

Further, it is preferable to control the oxygen content in a copper filmto not more than 50 ppm. When the oxygen content is controlled to notmore than 50 ppm, heat resistance is remarkably enhanced. Less than 50ppm oxygen, by contrast, enables a trace of element or elements toimpart remarkable heat resistance. This is presumably attributable tothe fact that a high oxygen content oxidized the alloying element addedand the resulting oxide no longer contributes to the heat resistance. Anoxygen content below 20 ppm is preferred.

The thickness of a copper foil generally has the range of 20 to 50 μm,but this invention is suitably applicable to a thinner foil having athickness of 15 to 30 μm.

Such rolled copper alloy foil is made by hot rolling an ingot having apredetermined composition, appropriately repeating cold rolling andannealing and then effecting final cold rolling to a thickness required.

It is preferred that the final cold rolling is followed by strain reliefannealing for the following reason. The reason is that material, as coldrolled, retains a large residual stress buildup inside. The stresses arereleased by the heat the material encounters during the fabrication intoa film carrier (e.g., the heat at the time of joining to the resin layeror at the time of etching pattern printing). This results in shrinkageof the copper alloy foil, which can lead to deformation. The strainrelief annealing that follows the final cold rolling is intended toprevent this deformation of leads to be formed from the copper alloyfoil. This is no special limitation to the procedure of strain reliefannealing; a suitable one of the conventional annealing methods may beused. For example, a treatment at 100° to 500° C. for 20 seconds to 1hour may be carried out.

Typical examples of tensile strengths and elongations of a copper alloyfoil for use in the present invention and a conventional tough pitchcopper foil will now be explained with reference to FIG. 2. Testspecimens of the copper alloy foil for use in the invention aredesignated Sn-containing (0.15% Sn) copper alloy foil specimens 8a, 8b,9a, and 9b, and comparative test specimens are those of a conventionaltough pitch copper, designated bright foil specimens 6a, 6b, 7a, and 7b.FIG. 2 clearly shows that the Sn-containing copper alloy foil specimens8a, 8b retain high tensile strength at annealing temperatures (15minutes) above 300° C.

The tensile strengths of the tough pitch copper foil specimens 6a, 6bare seen sharply declining at temperatures from about 120° C. upward,indicating very low heat-resisting strengths. This suggests seriouslylow reliability of the film carriers having leads made from theconventional heat-affected tough pitch rolled copper foil. With regardto the directionality of rolling, or the longitudinal (rolling)direction and lateral (normal to the rolling) direction, as can be seenwith the conventional tough pitch rolled copper foil specimens in FIG.2, there are marked differences in tensile strength (between thelongitudinal, 6a, and lateral, 6b, directions) and in elongation(between the longitudinal, 7a, and lateral, 7b, directions). Thedifferences are pronounced in the temperature region of 160° to 200° C.wherein the material is subjected to heat. A shift in position ordeformation due to such anisotropy adds to the inaccuracy of theconnection to components.

With the specimens of the Sn-containing copper foil as shown typicallyfor use in the present invention, the high heat resistance as mentionedabove is attained. Furthermore, practically no such anisotropy as withthe comparative foil in the longitudinal and lateral tensile strengths(8a and 8b) and elongations (9a and 9b). These properties contributegreatly to the reliability of the film carrier having fine leads in ahigh density pattern.

Similarly high heat resistance was attained with other alloycompositions for use in forming leads in accordance with the invention.

By the use of a high quality copper foil as described above, it becomespossible to manufacture a film carrier by which the density of multi-pinarrangement can be remarkably increased. As described previously, asubstrate or base film is made of a resin such as polyimide, polyester,polyether sulfone, polyparabanic acid etc. A continuous elongated basefilm is punctured to form sproket holes, device holes for containing ICtips or other devices etc. and a copper foil is laminated thereon with apolyester- or epoxy-based adhesive. Such film including an adhesivelayer is called three-layer film in the art. Thereafter, the copper foilis subjected to a series of treatments including printing, exposure,development and etching to form fine patterns as shown in FIG. 1. Then,as necessary, platings with gold, tin, lead, solder etc. are made toproduce a film carrier.

The material of the invention will be described more fully below inconnection with Examples thereof.

EXAMPLE 1

Alloys of varying compositions according to this invention, as listed inTable 1, were melted each in a high-frequency melting furnace and castinto an ingot each. Each ingot was hot rolled at 900° C. into an 8mm-thick plate and then cold rolled to a thickness of 1 mm. Theresulting sheet was annealed at 500° C. for one hour and cold rolled toa thickness of 0.2 mm. Further annealing at 500° C. for one hour andcold rolling yielded a 0.025 mm-thick foil.

Each test material thus prepared was evaluated by the following tests.Strength was determined in terms of tensile strengths measured in thedirections parallel and normal to the rolling direction. Heat resistancewas determined in terms of the softening temperature in a heating periodof 5 minutes. Electrical conductivity tested is expressed in % IACS.With each alloy foil a three-layer film carrier of a polyimide film wasactually made and inspected for any deformation of the fingers.

As Table 1 clearly shows, the alloys of the invention are excellent instrength, heat resistance, and conductivity. With only limitedanisotropy, the alloys give film carriers free from deformation. Theseproperties make them suitable as copper alloy foils for film carriers.

                                      TABLE 1                                     __________________________________________________________________________                         Tensile strength (kg/mm.sup.2)                                                                  Softening                                        Alloy composition (wt %)                                                                 parallel to                                                                            normal to                                                                              temperature                                                                           Conductivity                                                                          Deformation as                   Cu Element added                                                                         rolling direction                                                                      rolling direction                                                                      (°C.)                                                                          (% IACS)                                                                              film                   __________________________________________________________________________                                                           carrier                Alloy  1  bal.                                                                             P 0.01, Sn 0.1                                                                        48.3     48.5     350     88      No                     of the 2  "  B 0.02  48.1     48.0     350     94      "                      invention                                                                            3  "  Al 0.1  47.7     48.2     300     87      "                             4  "  Co 0.07 49.4     49.6     350     85      "                             5  "  In 0.1  51.8     52.4     350     95      "                             6  "  Fe 0.05, Mn 0.05                                                                      49.0     48.8     350     92      "                             7  "  Mg 0.06, Te 0.1                                                                       46.5     47.0     400     98      "                             8  "  Ni 0.1, P 0.008                                                                       50.4     50.2     375     91      "                             9  "  Cr 0.3, Si 0.03                                                                       53.0     53.1     425     88      "                             10 "  Ag 0.2  47.6     48.0     400     98      "                             11 "  Hf 0.02, Zr 0.15                                                                      52.3     52.6     475     96      "                             12 "  Te 0.2  45.0     45.3     400     97      "                             13 "  Zr 0.9, Si 0.2                                                                        55.7     56.5     500     90      "                             14 "  Zn 1.0, Sn 0.1                                                                        49.0     49.5     375     91      "                      Comparative                                                                          1  "  --      43.0     45.7     200     102     Yes                    alloy  2  "  P 0.003 44.8     45.5     200     95      "                             3  "  Sn 0.007                                                                              44.3     45.8     200     99      Yes (some)                    4  "  Fe 0.6, Al 0.2                                                                        57.0     58.2     500     52      No                            5  "  Zn 1.5, Ni 0.6                                                                        53.6     54.0     475     47      "                      __________________________________________________________________________

EXAMPLE 2

Alloys of varying compositions for the leads on the film carrieraccording to this invention, as listed in Table 2, were melted each in ahigh-frequency melting furnace and cast into an ingot each.

Next, each ingot was hot rolled at 900° C. into an 8 mm-thick plate andthen cold rolled to a thickness of 1 mm. The resulting sheet wasannealed at 500° C. for one hour and cold rolled to a 0.2 mm thickness.Further annealing at 500° C. for one hour and cold rolling yielded a0.025 mm-thick foil.

The foils were then annealed under the strain relief annealingconditions given in Table 2. Each test material thus prepared wasevaluated by the following tests. Strength was determined in terms oftensile strengths measured in the directions both parallel and normal tothe rolling direction. Heat resistance was determined in terms of thesoftening temperature in a heating period of one hour. Electricalconductivity tested is expressed in % IACS. With each alloy foil athree-layer tape carrier of a polyimide film was made and inspected forany deformation of the leads.

As Table 2 clearly shows, the alloys of the invention were excellent instrength, heat resistance, and conductivity. With only limitedanisotropy, the alloys give film carriers free from deformation of theleads. These properties make them suitable as copper alloy foils forfilm carriers.

                                      TABLE 2                                     __________________________________________________________________________                               Strain relief                                                                          Tensile                                                                             Softening                                     Alloy compositoin (wt %)                                                                       annealing                                                                              strength                                                                            temperature                                                                          Conductivity                                                                         percentage                      Cu  Element added                                                                              condition                                                                              (kg/mm.sup.2)                                                                       (°C.)                                                                         (% IACS)                                                                             Skrinage              __________________________________________________________________________    Alloy  1  bal.                                                                              P 0.01, Sn 0.12                                                                            200° C. × 3 min.                                                          47.8  300    85     0.003                 of the 2  "   B 0.01, Ag 0.1                                                                             300° C. × 1 "                                                             47.5  300    96     0.002                 invention                                                                            3  "   Al 0.05, As 0.02                                                                           200° C. × 2 "                                                             47.6  250    92     0.003                        4  "   In 0.1       200° C. × 3 "                                                             51.2  300    95     0.003                        5  "   Co 0.05, Te 0.1                                                                            250° C. × 1 "                                                             48.3  325    93     0.003                        6  "   Fe 0.05, Mn 0.05                                                                           200° C. × 2 "                                                             47.7  300    92     0.003                        7  "   Cr 0.1, Zr 0.05, Si 0.02                                                                   500° C. × 0.5 "                                                           52.0  350    88     0.002                        8  "   Ni 0.1, Zn 0.4                                                                             200° C. × 2 "                                                             46.2  275    92     0.003                        9  "   Mg 0.06, Hf 0.03, Cd 0.01                                                                  250° C. × 3 "                                                             47.6  300    94     0.003                 Comparative                                                                          1  "   P 0.01, Sn 0.12                                                                            --       48.7  300    86     0.040                 alloy  2  "   B 0.01, Ag 0.1                                                                             --       48.0  300    96     0.038                        3  "   Al 0.05, As 0.02                                                                           --       48.2  250    92     0.038                        4  "   In 0.1       --       51.8  300    95     0.040                        5  "   Co 0.05, Te 0.1                                                                            --       49.1  325    93     0.042                        6  "   Fe 0.05, Mn 0.05                                                                           --       49.0  300    92     0.043                        7  "   Cr 0.1, Zr 0.05, Si 0.02                                                                   --       52.0  350    88     0.040                        8  "   Ni 0.1, Zn 0.4                                                                             --       47.5  275    92     0.039                        9  "   Mg 0.06, Hf 0.03, Cd 0.01                                                                  --       48.0  300    94     0.043                 __________________________________________________________________________

EXAMPLE 3

Alloys of varying compositions for the leads on the film carrieraccording to this invention, as listed in Table 3, were melted each in ahigh-frequency melting furnace and cast into an ingot each. In order tolimit the oxygen content to 50 ppm or less, a copper material containingnot more than 50 ppm oxygen, termed oxygen-free or low-oxygen copper, isused and the alloy is melted and cast in a reducing or inert atmosphereto avoid the oxidation of copper. Each ingot was hot rolled at 900° C.into an 8 mm-thick plate and then cold rolled to a thickness of 1 mm.The resulting sheet was annealed at 500° C. for one hour and cold rolledto a 0.2 mm thickness. Further annealing at 500° C. for one hour andcold rolling yielded a 0.025 mm-thick foil.

Each test material thus prepared was evaluated by the following tests.Strength was determined in terms of tensile strengths measured in thedirections both parallel and normal to the rolling direction. Heatresistance was determined in terms of the softening temperature in aheating period of one hour. Electrical conductivity tested in expressedin % IACS. With each alloy foil a three-layer film carrier of apolyimide film was made and inspected for any deformation of the leads.

As Table 3 clearly shows, the alloys of the invention were excellent instrength, heat resistance, and conductivity. With only limitedanisotropy, the alloys give film carriers free from deformation. Theseproperties make them suitable as copper alloy foils for film carriers.

Other samples of the invention subjected to strain relief annealing aregiven in Table 4. The Table 4 shows the shrinkage percentages of leadmembers of two alloy compositions, with strain relief annealing (Testspecimen Nos. 1 and 2) and without (Nos. 3 and 4), under the influenceof heat to be possibly encountered (200° C. for 10 minutes). As is clearfrom Table 4, the stress rel annealed specimens shrank only one-tenth orless the percentages of those not annealed. Similar tendencies werenoted with the other copper alloy compositions for use in making thefilm carriers according to the invention. The shrinkage of the leadmembers does not always cause deformation of the film carriers, but itcan be a factor that induces or promotes the deformation. Strain reliefannealing, therefore, is desirable.

                                      TABLE 3                                     __________________________________________________________________________                                 Tensile                                                                       strength (kg/mm.sup.2)                                                        Parallel                                                                            Normal                                                                              Softenging                                      Alloy composition (wt %)                                                                        to rolling                                                                          to rolling                                                                          temperature                                                                          Conductivity                                                                         Deformation as                    Cu  Element added                                                                          Oxygen                                                                             direction                                                                           direction                                                                           (°C.)                                                                         (% IACS)                                                                             film                   __________________________________________________________________________                                                           carrier                Alloy  1   bal.                                                                              P 0.01, Sn 0.1                                                                         0.0018                                                                             48.3  48.5  300    88     No                     of the 2   "   B 0.02   0.0035                                                                             48.1  48.0  275    94     "                      invention                                                                            3   "   Al 0.05, As 0.02                                                                       0.0020                                                                             48.2  48.6  250    92     "                             4   "   Co 0.05  0.0042                                                                             48.7  49.0  300    97     "                             5   "   In 0.1   0.0011                                                                             51.8  52.4  300    95     "                             6   "   Fe 0.05, Mn 0.05                                                                       0.0016                                                                             49.0  48.8  300    92     "                             7   "   Mg 0.06, Cd 0.03                                                                       0.0008                                                                             47.0  47.5  275    96     "                             8   "   Ni 0.1, P 0.008                                                                        0.0015                                                                             50.4  50.2  300    91     "                             9   "   Cr 0.3, Si 0.03                                                                        0.0010                                                                             51.5  51.7  350    92     "                             10  "   Ag 0.2   0.0032                                                                             47.6  48.0  350    98     "                             11  "   Hf 0.03, Zr 0.1                                                                        0.0010                                                                             50.3  50.5  350    97     "                             12  "   Te 0.2   0.0017                                                                             45.0  45.3  350    97     "                             13  "   Zr 0.9, Si 0.2                                                                         0.0006                                                                             55.7  56.5  450    90     "                             14  "   Zn 0.4, Sn 0.1                                                                         0.0014                                                                             48.0  48.2  300    94     "                      Comparative                                                                          1   "   --       0.0010                                                                             43.0  45.7  140    102    Yes                    alloy  2   "   Sn 0.1   0.0153                                                                             47.3  47.8  220    98     Slight                        3   "   In 0.1   0.0115                                                                             50.7  51.4  180    95     Yes                           4   "   Hf 0.03, Zr 0.1                                                                        0.0067                                                                             49.2  49.5  225    97     Slight                        5   "   Zn 1.5, Ni 0.6                                                                         0.0025                                                                             53.6  54.0  350    47     No                     __________________________________________________________________________

                  TABLE 4                                                         ______________________________________                                                                          Percentage                                  Test  Alloy Composition           of*                                         speci-                                                                              (wt %)           Strain relief                                                                            shrinkage                                   men          Element         annealing                                                                              on heating                              No.   Cu     added    Oxygen condition                                                                              (%)                                     ______________________________________                                        1     bal.   P 0.01   0.0018 200° C. ×                                                                 0.003                                                Sn 0.1          3 min.                                           2     bal.   In 0.1   0.0011 300° C. ×                                                                 0.003                                                                1 min.                                           3     bal.   P 0.01   0.0018 --       0.035                                                Sn 0.1                                                           4     bal.   In 0.1   0.0011 --       0.003                                   ______________________________________                                         *Percentage of shrinking on heating at 200° C. for 10 min.        

ADVANTAGEOUS EFFECTS OF THE INVENTION

Film carriers capable of achieving greater packaging densities thanheretofore required of the leads are under development to keep up withthe rapid tendency toward multipin arrangements along with theincreasing degrees of integration for ICs, LSIs, and the like. The finerand narrower arrangements and configurations of leads are posingdeformation, shorting, anisotropy, and other very serious problems. Thisinvention has now solved all these problems and contributes greatly tothe technical progress in the art and to the realization of an excellentfilm carrier, and further to its manufacture.

What we claim is:
 1. A film carrier comprising a resin base film and arolled copper foil laminated thereon, said rolled copper foil formingleads for mounting semiconductor chips or other electronic components inplace, characterized in that said rolled copper foil is made of a copperalloy composition consisting essentially of a total of 0.005 to 1.5% byweight of one or more selected from the group consisting of

    ______________________________________                                        P     0.005-0.05                                                                              wt %,    B    0.005-0.05                                                                             wt %,                                  Al    0.01-0.5  wt %,    As   0.01-0.5 wt %                                   Cd    0.01-0.5  wt %,    Co   0.01-0.5 wt %,                                  Fe    0.01-0.5  wt %,    In   0.01-0.5 wt %,                                  Mg    0.01 = 0.5                                                                              wt %,    Mn   0.05-0.2 wt %,                                  Ni    0.01-0.5  wt %,    Si   0.01-0.5 wt %,                                  Sn    0.01-0.5  wt %,    Te   0.01-0.5 wt %,                                  Ag    0.01-1    wt %,    Cr   0.01-1   wt %,                                  Hf    0.01-1    wt %,    Zn   0.01-1   wt % and                               Zr    0.01-1    wt %,                                                         ______________________________________                                    

and the remainder Cu with inevitable impurities.
 2. The film carrieraccording to the claim 1 wherein the content of oxygen is not more than50 ppm.
 3. The film carrier according to claim 1 wherein said rolledcopper foil comprises a copper alloy composition consisting essentiallyof one or more elements selected from the group consisting of In, Sn andAg and the remainder Cu with inevitable impurities.
 4. The film carrieraccording to claim 3 wherein the content of oxygen is not more than 50ppm.
 5. The film carrier according to claim 4 wherein the content ofoxygen is less than 20 ppm.
 6. A film carrier comprising a resin basefilm and a rolled copper foil laminated thereon, said rolled copper foilforming leads for mounting semiconductor chips or other electroniccomponents in place, characterized in that said rolled copper foil ismade of a copper alloy composition consisting essentially of a total of0.005 to 1.5% by weight of one or more selected from the groupconsisting of

    ______________________________________                                        P     0.007-0.02                                                                              wt %,    B    0.007-0.02                                                                             wt %,                                  Al    0.05-0.2  wt %,    As   0.05-0.2 wt %                                   Cd    0.05-0.2  wt %,    Co   0.05-0.2 wt %,                                  Fe    0.05-0.2  wt %,    In   0.02-0.2 wt %,                                  Mg    0.05-0.2  wt %,    Mn   0.05-0.2 wt %,                                  Ni    0.05-0.2  wt %,    Si   0.05-0.2 wt %,                                  Sn    0.05-0.2  wt %,    Te   0.05-0.2 wt %,                                  Ag    0.05-0.5  wt %,    Cr   0.05-0.5 wt %,                                  Hf    0.05-0.5  wt %,    Zn   0.1-0.8  wt %, and                              Zr    0.05-0.5  wt %,                                                         ______________________________________                                    

and the remainder Cu with inevitable impurities.
 7. A film carrieraccording to claim 6 wherein said copper alloy composition consistsessentially of a total of 0.005 to 1.5% by weight of at least oneelement selected from the group consisting of In, Sn and Ag.
 8. A filmcarrier according to claim 6 wherein the content of oxygen is not morethan 50 ppm.
 9. A film carrier according to claim 6 wherein the contentof oxygen is not more than 20 ppm.